Fabric soaking operations have been described in the art. In such soaking operations, fabrics are left in contact with a soaking liquor for a prolonged period of time ranging from a few hours to overnight. This laundering process has the advantage that it maximizes the contact time between the fabrics and the key active ingredients of the soaking liquor. It also has the advantage that it reduces or eliminates the need for a typical laundering operation involving the need for mechanical agitation, or that it improves the efficiency of the subsequent typical laundering operation.
Such soaking operations are typically efficient to remove tough stains such as blood and food stains, which comprise a blend of proteic substances as well as starch. Thus it is desirable that soaking compositions should comprise a protease as well as an amylase. However with such a soaking composition, amylases themselves are subject to proteolytic attack, as the soaking composition is dissolved to form a soaking liquor. This is a particularly acute problem in the context of soaking, where the contact time between the ingredients in general, the amylase and the protease in particular, is generally enormously longer than in typical laundering operation. Thus it is one object of the present composition to provide soaking compositions which comprise an amylase and a protease, and where the amylase will resist proteolytic attack for a significant period of time.
Another requirement of soaking compositions is that they should comprise an oxygen bleach, preferably a high amount of such a bleach. Indeed, an oxygen bleach finds suitable conditions for efficacy in a soaking operation where, contact time between the actives of the compositions and the soiled fabrics is maximized. However, the presence of bleach is also detrimental to the stability of the enzymes throughout the period of the soaking operation. Indeed bleaches, especially at high level tend to denature the quaternary stucture of the enzymes, exposing amylase to an even more aggressive proteolytic attack.
Still another requirement of soaking compositions is that they should comprise significant amounts of builders. Indeed the presence of builders is necessary to effectively control water hardness. Builders are even more necessary in soaking conditions where contact time between fabrics and wash solution is longer, as compared to normal washes, thus hardness must be controlled for a much longer time. To comply with the peculiarities of the soaking process, soaking compositions must therefore contain high levels of builders. However, the presence of high levels of builders is also detrimental to the action of enzymes. Indeed, these builders tend to bind all the calcium present in the soak solution, amongst other things, while some calcium is needed to ensure appropriate enzyme activity.
Finally, another requirement of soaking compositions is that they should comprise significant amounts of an anionic surfactant. A preferred anionic surfactant class, for cost and performance reasons is alkylbenzene sulphonate, particularly linear ones. Certain anionic surfactants, linear alkylbenzene sulphonates (LAS) in particular, however appear to be detrimental to enzyme stability.
It is thus an object of the present invention to provide a soaking composition suitable for a soaking operation, which comprises an amylase in combination with a protease, a bleaching system, a high amount of a builder, and an anionic surfactant, preferably LAS, wherein said amylase remains active for a long period of time, consitent with the characteristics of a soaking operation.